22,346 research outputs found

### String and Fivebrane Solitons: Singular or Non-singular?

We ask whether the recently discovered superstring and superfivebrane
solutions of D=10 supergravity admit the interpretation of non-singular
solitons even though, in the absence of Yang-Mills fields, they exhibit
curvature singularities at the origin. We answer the question using a test
probe/source approach, and find that the nature of the singularity is
probe-dependent. If the test probe and source are both superstrings or both
superfivebranes, one falls into the other in a finite proper time and the
singularity is real, whereas if one is a superstring and the other a
superfivebrane it takes an infinite proper time (the force is repulsive!) and
the singularity is harmless. Black strings and fivebranes, on the other hand,
always display real singularities.Comment: 15 page

### Macroscopic superstrings as interpolating solitons

It is known that, in string sigma-model metric, the `extreme' fivebrane
solution of D=10 supergravity interpolates between D=10 Minkowski spacetime and
a supersymmetric $S^3$ compactification to a linear dilaton vacuum. We show
here that, in {\it fivebrane} sigma-model metric, the extreme string solution
of D=10 supergravity interpolates between Minkowski spacetime and a hitherto
unknown supersymmetric $S^7$ compactification of d=10 supergravity to a
three-dimensional anti-de Sitter generalization of the linear dilaton vacuum,
which may be invariantly characterized in terms of conformal
Killing vectors. The dilaton field diverges near the string core but this
divergence may be eliminated by re-interpreting the string solution as the
extreme membrane solution of 11-dimensional supergravity. We show that the
latter has an analytic extension through a regular degenerate event horizon to
an interior region containing a curvature singularity. We obtain analogous
results for other extended object solutions of supergravity theories.Comment: 12 page

### Hodge Duality on the Brane

It has been claimed that whereas scalars can be bound to a Randall-Sundrum
brane, higher p-form potentials cannot, in contradiction with the Hodge duality
between 0-form and 3-form potentials in the five-dimensional bulk. Here we show
that a 3-form in the bulk correctly yields a 2-form on the brane, in complete
agreement with both bulk and brane duality. We also emphasize that the
phenomenon of photon screening in the Randall-Sundrum geometry is ruled out by
the bulk Einstein equation.Comment: 6 pages, Latex. We emphasize that the phenomenon of photon screening
in the Randall-Sundrum geometry is ruled out by the bulk Einstein equatio

### On the determination of the dilaton-antisymmetric tensor couplings in supergravity theories

A new approach is provided to determine the dilaton--antisymmetric tensor
coupling in a supergravity theory by considering the static supersymmetric
field configuration around a super extended object, which is consistently
formulated in a curved superspace. By this, the corresponding SUSY
transformation rules can also be determined for vanishing fermionic fields as
well as bosonic fields other than those in the determined coupling. Therefore,
we can, in turn, use this determined part of the supergravity theory to study
all the related vacuum-like solutions. We have determined the
dilaton--antisymmetric tensor couplings, in which each of the antisymmetric
tensors is a singlet of the automorphism group of the corresponding
superalgebra, for every supergravity multiplet. This actually happens only for
$N \leq 2$ supergravity theories, which agrees completely with the spin-content
analysis and the classified $N \leq 2$ super $p$-branes, therefore giving more
support to the existence of the fundamental Type II $p$-branes. A prediction is
made of the $D = 9, N = 2$ supergravity which has not yet been written down so
far.Comment: 23 pages, harvmac, CERN-TH.6691/9

### Evidence for Heterotic/Heterotic Duality

We re-examine the question of heterotic - heterotic string duality in six
dimensions and argue that the $E_8\times E_8$ heterotic string, compactified on
$K3$ with equal instanton numbers in the two $E_8$'s, has a self-duality that
inverts the coupling, dualizes the antisymmetric tensor, acts non-trivially on
the hypermultiplets, and exchanges gauge fields that can be seen in
perturbation theory with gauge fields of a non-perturbative origin. The special
role of the symmetric embedding of the anomaly in the two $E_8$'s can be seen
from field theory considerations or from an eleven-dimensional point of view.
The duality can be deduced by looking in two different ways at
eleven-dimensional $M$-theory compactified on $K3\times {\bf S}^1/\Z_2$.Comment: 36 pages, LaTe

### Four Dimensional String/String/String Triality

In six spacetime dimensions, the heterotic string is dual to a Type $IIA$
string. On further toroidal compactification to four spacetime dimensions, the
heterotic string acquires an SL(2,\BbbZ)_S strong/weak coupling duality and
an SL(2,\BbbZ)_T \times SL(2,\BbbZ)_U target space duality acting on the
dilaton/axion, complex Kahler form and the complex structure fields $S,T,U$
respectively. Strong/weak duality in $D=6$ interchanges the roles of $S$ and
$T$ in $D=4$ yielding a Type $IIA$ string with fields $T,S,U$. This suggests
the existence of a third string (whose six-dimensional interpretation is more
obscure) that interchanges the roles of $S$ and $U$. It corresponds in fact to
a Type $IIB$ string with fields $U,T,S$ leading to a four-dimensional
string/string/string triality. Since SL(2,\BbbZ)_S is perturbative for the
Type $IIB$ string, this $D=4$ triality implies $S$-duality for the heterotic
string and thus fills a gap left by $D=6$ duality. For all three strings the
total symmetry is SL(2,\BbbZ)_S \times O(6,22;\BbbZ)_{TU}. The
O(6,22;\BbbZ) is {\it perturbative} for the heterotic string but contains the
conjectured {\it non-perturbative} SL(2,\BbbZ)_X, where $X$ is the complex
scalar of the $D=10$ Type $IIB$ string. Thus four-dimensional triality also
provides a (post-compactification) justification for this conjecture. We
interpret the $N=4$ Bogomol'nyi spectrum from all three points of view. In
particular we generalize the Sen-Schwarz formula for short multiplets to
include intermediate multiplets also and discuss the corresponding black hole
spectrum both for the $N=4$ theory and for a truncated $S$--$T$--$U$ symmetric
$N=2$ theory. Just as the first two strings are described by the
four-dimensional {\it elementary} and {\it dual solitonic} solutions, so theComment: 36 pages, Latex, 2 figures, some references changed, minor changes in
formulas and tables; to appear in Nucl. Phys.

### g=1 for Dirichlet 0-branes

Dirichlet 0-branes, considered as extreme Type IIA black holes with spin
carried by fermionic hair, are shown to have the anomalous gyromagnetic ratio
g=1, consistent with their interpretation as Kaluza-Klein modes.Comment: 13 pages, Late

### The Coupling of Yang-Mills to Extended Objects

The coupling of Yang-Mills fields to the heterotic string in bosonic
formulation is generalized to extended objects of higher dimension (p-branes).
For odd p, the Bianchi identities obeyed by the field strengths of the
(p+1)-forms receive Chern-Simons corrections which, in the case of the 5-brane,
are consistent with an earlier conjecture based on string/5-brane duality.Comment: 14 Page

### The Octonionic Membrane

We generalize the supermembrane solution of D=11 supergravity by permitting
the 4-form $G$ to be either self-dual or anti-self-dual in the eight dimensions
transverse to the membrane. After analyzing the supergravity field equations
directly, and also discussing necessary conditions for unbroken supersymmetry,
we focus on two specific, related solutions. The self-dual solution is not
asymptotically flat. The anti-self-dual solution is asymptotically flat, has
finite mass per unit area and saturates the same mass=charge Bogomolnyi bound
as the usual supermembrane. Nevertheless, neither solution preserves any
supersymmetry. Both solutions involve the octonionic structure constants but,
perhaps surprisingly, they are unrelated to the octonionic instanton 2-form
$F$, for which $TrF \wedge F$ is neither self-dual nor anti-self-dual.Comment: 17 pages, Latex; enhanced discussion on supersymmetry, some
references adde

### p-brane Solitons in Maximal Supergravities

In this paper, we give a construction of $p$-brane solitons in all maximal
supergravity theories in $4\le D \le 11$ dimensions that are obtainable from
$D=11$ supergravity by dimensional reduction. We first obtain the full bosonic
Lagrangians for all these theories in a formalism adapted to the $p$-brane
soliton construction. The solutions that we consider involve one dilaton field
and one antisymmetric tensor field strength, which are in general linear
combinations of the basic fields of the supergravity theories. We also study
the supersymmetry properties of the solutions by calculating the eigenvalues of
the Bogomol'nyi matrices, which are derived from the commutators of the
supercharges. We give an exhaustive list of the supersymmetric $p$-brane
solutions using field strengths of all degrees $n=4,3,2,1$, and the
non-supersymmetric solutions for $n=4,3,2$. As well as studying elementary and
solitonic solutions, we also discuss dyonic solutions in $D=6$ and $D=4$. In
particular, we find that the Bogomol'nyi matrices for the supersymmetric
massless dyonic solutions have indefinite signature.Comment: 31 pages, Latex, no figure

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